1. Field of the Invention
The invention relates to an ink jet recording head for recording images and characters on recording paper by jetting ink droplets out of nozzle openings through the expansion and contraction of piezoelectric vibration elements of a vertical vibration mode. More specifically, the invention is directed to a piezoelectric vibration element mounting structure.
2. Background
Ink jet recording heads in which not only nozzle openings and portions of pressure producing chambers communicating with a reservoir are formed by a resilient plate, but also each pressure producing chamber is expanded and contracted by resiliently deforming the resilient plate through a piezoelectric vibration element which expands and contracts in the axial direction are advantageous in downsizing the structure and increasing the operating speed compared with recording heads based on flexural vibration in which the resilient plate is deformed toward a surface.
FIG. 8 shows an exemplary ink jet recording head using the piezoelectric vibration element of the vertical vibration mode. In FIG. 8, reference numeral 50 denotes a piezoelectric vibration element of the vertical vibration mode, which is formed by alternatingly laminating electrically conducting layers 51, 52 and a piezoelectric material layer 53. A lateral portion of an inactive region at the rear end of the piezoelectric vibration element 50 is fixed to a frame 55 with an adhesive through a fixed board 54, and the front end of the piezoelectric vibration element is fixed to an island portion 58 of a resilient plate 57 defining pressure producing chamber 56.
The resilient plate 57, a flow path forming plate 61, and a nozzle plate 63 are assembled into an ink jet recording head while laminated and fixed to a surface 60 of the frame 55. It should be noted that reference numerals 65, 65 denote thin-walled portions formed along the peripheral edges of the island portion 58.
However, with this construction, distortion caused by a difference in the thermal expansion coefficients of the ceramic of which the piezoelectric vibration element 50 is made and of the material of which the frame 55 is made, e.g., plastic, is exhibited substantially in proportion to the length L of the piezoelectric vibration element 50. If both the piezoelectric vibration element 50 and the frame 55 are to be bonded together at a higher temperature to obtain stronger adhesive bonding in consideration of the distortion, a temperature difference between the bonding temperature and the operating temperature of 40.degree. C. is produced. As a result, at the operating temperature, a thermal expansion difference of about: 10 .mu.m is produced if the effective length L of the piezoelectric vibration element 50 is set to 5.5 mm, thereby destroying the resilient plate 57 or destroying an adhesive between the frame and the resilient plate.
To overcome this problem, one possibility is to make the frame 55 of a ceramic that has the same characteristics as the material of which the piezoelectric vibration element 50 is made. However, this complicates the working process and hence increases the cost of manufacture.